(An email from a reader commenting on my Wire last week prompted this column.)

It's important to recognize that all your actions – from the time you touch your weapon, draw it or if necessary fire – will have to be justified. It will be necessary to explain why you did what you did.

Massad Ayoob uses the terms "Ability, Opportunity and Jeopardy." The offender(s) must have the "ability" to do you harm, using a weapon or through their physical actions. There must be an "opportunity" for them to immediately use that ability – e..g., they have a knife and are close enough to use it. Finally, their actions create "jeopardy." You are about to be on the receiving end of serious bodily harm/injury or death. All three of these elements must be present for you to be justified in presenting your weapon, much less using it against someone.

In order to understand this it's necessary to know the law, which can vary greatly from one state to another or sometimes city to city. Legally, when and why can you draw your weapon? Feeling uneasy or nervous is not enough. Remember, depending on where you are the act drawing a weapon, or even making the motions to draw, without good reason is a serious crime.

Did they have a weapon? Sometimes it will be easy to see that the threat is armed. Other times someone's body language - "furtive" actions – is consistent with one who is armed. The majority of our communication is non-verbal. You have to learn what people are "saying" through their physical actions. Was a successful physical assault possible? A younger man with powerful muscles who outweighs me by fifty pounds is easily capable of causing me serious harm. I'm not going to easily be able to justify why I thought an unarmed eighty pound teenager could physically overwhelm me. There is a lot of gray in-between the two opposite ends of the spectrum.

And don't think that you'll be able to lie about what occurred. There's a big chance there will be witnesses, and today everyone is quick to video the action. In urban areas, cameras monitor a lot of the environment. Physical evidence tells what occurred. The truth is going to surface. Fabricating a story to fit your actions is going to get you in trouble. Tell the truth.

If forced to draw your weapon, even if you didn't have to use it, contact the authorities as soon as possible to report your actions. I've actually had people tell me that if something happens and nobody is around to see it that they will not call the authorities. This is a bad idea. Again, there will probably be witnesses/video, even if you don't see someone. Plus, you don't want the threat calling in a false report - "There's a man in blue jeans and a tan shirt threatening people with his gun!" Report your actions immediately.

Knowing the law is mandatory, but it's also important to be morally justified. People will explain the "Castle Doctrine" this way: "If someone is in my house I can shoot them." This way of thinking leads to the wrongful shooting of family members, friends and people who just entered the wrong house by mistake. Even if they are in your house and dangerous, avoidance and escape are your best tactics. Just because someone is in your house does not legally or morally justify you shooting them.

The responsibilities of owning a firearm for self-defense are enormous. You do everything possible to avoid locations where it might be needed. Just because you draw it doesn't mean you will need to shoot. Anytime something occurs involving the use of that weapon, you have a duty to justify your actions. Make sure you know what to do, and the legal justifications for your actions.